Humans breath more than one cubic meter of air every hour, and the large quantities of particles, antigens, infectious agents and toxic gases and fumes that are present in inhaled air are usually dealt with by the lung. The interaction of these particles with the immune system and other lung defense mechanisms results in the generation of a controlled inflammatory response which is usually protective and beneficial. In general, this process regulates itself in order to preserve the integrity of the airway and alveolar epithelial surfaces where gas exchange occurs.
In some cases, however, the inflammatory response cannot be regulated and the potential for tissue injury is increased. Depending on the type of environmental exposure, genetic predisposition, and a variety of ill-defined factors, abnormally large numbers of inflammatory cells can be recruited at different sites of the respiratory system, resulting in illness or disease.
The inflammatory response to inhaled or intrinsic stimuli is characterized by a non-specific increase in the vascular permeability, the release of inflammatory and chemotactic mediators including histamine, eicosanoids, prostaglandins, cytokines and chemokines. These mediators modulate the expression and engagement of leukocyte-endothelium cell adhesion molecules allowing the recruitment of inflammatory cells present in blood.
A more specific inflammatory reaction involves the recognition and the mounting of an exacerbated, specific immune response to inhaled antigens. This reaction is involved in the development of asthma, Hypersensitivity pneumonitis (HP) and possibly sarcoidosis. Dysregulation in the repair mechanisms following lung injury may contribute to fibrosis and loss of function in asthma, pulmonary fibrosis, chronic obstructive pulmonary disease (COPD), and chronic HP.
Despite advances in the treatment of inflammatory illnesses, including pulmonary inflammatory diseases, treatment using available drugs or agents frequently results in undesirable side effects. For example, the inflammation of COPD is apparently resistant to corticosteroids, and consequently the need for the development of new anti-inflammatory drugs to treat this condition has been recognized. Similarly, while corticosteroids and other immunosuppressive medications have been routinely employed to treat pulmonary fibrosis, they have demonstrated only marginal efficacy. There is thus a need for new and reliable methods of treating inflammatory diseases, including pulmonary inflammatory diseases.